The present invention relates to a traction coefficient measurement device.
A power transmission means used in various machines and apparatus comprises a friction transmission or traction drive transmission, and a traction coefficient measurement device is utilized to measure a traction coefficient which affects the essential performance of the friction transmission or traction drive transmission.
For example, as a transmission for automobiles, helicopters, or ships, the utilization of an endless transmission of the toroidal type, that is a kind of traction drive transmission, is developed. In addition, the traction drive transmission is used for a spindle of the machine tools.
The traction drive transmission has a traction section that is an engagement portion where power transmitting members are provided in friction-engagement with each other, and the measurement of the traction coefficient of the traction section is important for design of the high performance traction drive transmission.
Conventionally used for this purpose is a traction coefficient measurement device which has a pair of rollers, that is driving roller and driven roller installed therein, the peripheral surfaces of which are engaged with each other for transmitting a rotational force.
There are two methods for measuring the traction coefficient using a pair of rollers.
In the first method, a driving roller drives a driven roller to rotate with, a load applied thereto, and slippage rate in the traction section is obtained from the rotation number of the driving and driven rollers, while the traction force is obtained in the traction section from the torque applied to the driving roller.
In the second method, a pair of rollers are driven to rotate with a different rotation number or peripheral speed, and a predetermined slippage rate is forcibly added to the traction section, and the traction force at the traction section is obtained from the torque applied to the driving roller.
In the methods mentioned above for measuring the traction force, one of the drive shaft and driven shaft, the drive shaft rotating with the driving roller and the driven shaft rotating with the driven roller, is fixed in position while the other shaft is supported so as to move to and from the one shaft. While the other shaft is forced against the one shaft through a press device, the traction force is measured.
For this measurement, the traction coefficient measurement device has a surface plate, and a support plate which is provided to rotatably support the other shaft on its upper surface, such that the support plate is movable in parallel on the surface plate in a horizontal direction by way of a translation bearing such as a linear guide or cross guide, or by way of a journal bearing with an oil film used therebetween.
In the case of the conventional traction coefficient measurement device, the driving shaft and the driven shaft are positioned at the same level in height. Accordingly, the tangent line with respect to the outer peripheral surfaces of the driving roller and driven roller extends vertically, and as the outer peripheral surfaces thereof are forced against each other, the force in the traction section is exerted in a horizontal direction.
The support plate,is provided on the upper surface of the surface plate such that it is movable in the horizontal direction by way of the translation bearing, as mentioned above, and may vibrate when any outside force is applied to it because a clearance is present within the translation bearing or an oil film is present in the journal bearing.
Specifically, in the conventional structure, the force of the press apparatus added to the other shaft as mentioned above is not intended to be utilized for stabilizing the support plate. Accordingly, the support plate may not be stable, and may vibrate during the measurement operation. Once it vibrates, the measurement results of the traction force and the traction coefficient calculated on the basis of the traction force may not be precise.
One objective of the present invention is to provide a traction coefficient measurement device by which it is possible to obtain a precise traction coefficient preventing vibration from occurring in the support plate as mentioned above.
Another objective of the present invention is to provide a traction coefficient measurement device wherein the traction coefficient can be precisely measured under a condition near the practical condition of the endless transmission of the toroidal type for automobiles.